Hey, Josh. Welcome to the boards. I did an edit of your bomb to help illustrate some crits... hope you don't mind:

The main problem here, I think, is lack of contrast. Your shades are very close together here, giving the piece a dull, kind of flat look. Given the proximity of the light source to the bomb (The most logical lightsource being the spark/flame deal).
The light source/shading was the second big change here. Like I said, the spark would be the most logical light source, but in you picture, the light appears to be coming from the bottom left hand side, as opposed to the upper right. I also altered the shading a bit to give the bomb more depth, basically meaning I make the highlights/shadows form more of a circular pattern... if that makes sense.
Finally, I changed the palette. As a general rule, straight greys are kinds bland, and shifting hues usually makes a piece more visually appealing. Note here how the pallet basically shifts from purple (in the shadows) to green-blue (highlights). It's a shift towards the yellow end of the spectrum, as the lightsource seems to have a yellow tint... I thought it made sense

I dunno...
The lines here, I didn't change at all. They were solid to begin with, so there was no need

. Last thing... I apologize in advance, as I'm sure this is long and (unintentionally) rambling. I'm... incredibly tired at the moment, and at work, and... losing focus, so if it's really garbled, just let me know and I'll try to clarify... Anyway, keep pixelling! It's always great to see people getting into it.